How does the Occupational Safety and Health Administration limit industrial noise exposure?

The Occupational Safety and Health Administration (OSHA) regulates industrial noise exposure under the Occupational Safety and Health Act of 1970. To protect workers, the agency establishes specific criteria that limit both the intensity of sound and the duration of exposure.1

OSHA determines compliance by calculating a worker's total daily noise dose (D). This is derived from the relationship:

$$D=\left(\frac{C_1}{T_1}\right)+\left(\frac{C_2}{T_2}\right)+\left(\frac{C_3}{T_3}\right)+\dots$$

In this formula, C represents the actual time spent at a specific noise level, and T represents the allowable time of exposure for that intensity. The maximum allowable daily dose is 1; any exposure resulting in a value greater than 1 is considered unacceptable.1

While hearing loss typically does not occur at sound pressure levels below 80 dBA, eight-hour exposure levels are generally recommended to be kept below 85 dBA to prevent hearing loss. When noise levels exceed safe limits, employers may be required to implement engineering controls, such as enclosing noisy machinery, or provide effective hearing protection to ensure worker safety.32